Sorry the other fan is there to control the temperature as I will be growing in a 1.2x1.2 tent running a 600w hps, using only an extraction and the vents on the tent I may run into heat issues and by using 2 fans I will get more air circulation keepong the tent cooler, saying its only to provide fresh air in is my mistake (saying this not knowing I'm correct) but I'm certain this is the case feel free to correct me